my car feeling kind of slow so i decided to start putting some mods on my s4 N/A.
everything that i have heard is that if you want to get anywhere at all with a n/a
that you had to make sure to have a nice freeflowing exhaust but that it would make my aux ports not work without proper backpressure. so i had kind of given up on the whole exhaust idea. well as i went through some of the fixes some people had done to resolve the aux port issue i noticed that one of the plans sounded like this weird bathroom fitting on my air pump. so i went and checked it out and it was the air pump aux fix but it had been opened to the point that it didn't open the ports. so i turned it to about halfway......... and.... wow i now know what working aux ports feel like hahahaha much better than before to say the least. i still am gonna go ahead with my plans to put a few more horses in my car.


so..... does this give me a blank check to make my exhaust as free flowing as i want to??? header no cats free flowing mufflers and all that?

 

As long as you have a split air pipe you should still get some function out of them. Maybe not full function, but better than nothing. Whatever is lost will be made up by the exhaust. Go with the Racing Beat header and cat delete pipe. Free flowing and designed to operate the ports properly. Then you can just use whatever Y pipe and muffler you want.

 

the point of the post is that i have a completely stock exhaust but for some reason the previous owner of the car hooked up my aux ports to the air pump and not to the exhaust at all. so now that i figured that out my ports work and they have no reliance on the exhaust backpressure at all. but the real question is why? why would someone route the ports to the air pump when they have a completely stock exhaust??? i mean it seems like a lot of work for nothing doesn't it? but the upside is i dont have to do it now haha yay!

 

Maybe they had an exhaust but canceled the install...

 

Maybe they returned the car close to stock to sell it...

 

Oh well at least it is already done for you. So yeah go ahead and put any exhaust you want on it.

 

Because sometimes the aux port actuators won't work, even with a stock exhaust system. The backpressure method sucks. Activating them via the air pump is much more predictable (granted using an RPM switch and solenoid would be better). You'll have to figure out what RPM this little valve is allowing them to open at. Free-rev the engine and have someone watch the tach.

 

the setup has a little valve on the side of it so that i can tune when i want the ports to open. i have been testing it recently and i can go all the way from the ports not opening at all to having them open at 2500 rpm. after some trial and error testing i found that it feels the best to me when i have them start to open at 4200 rpm. i plan on getting new mufflers and straightpiping the cats in the very near future.